Method of manufacturing propellers



June 16, 1936. D R 2,044,293

METHOD OF MANUFACTURING PROPELLERS Filed Au 19, 1929 T gwoantoz Patented June 16, 1936 METHOD OF MANUFACTURING PROPELLERS Alfred A. Handler, Cleveland, Ohio, assignor to Aluminum Company of America, a corporation of Pennsylvania Application August 19, 1929, Serial No. 387,017 15 Claims. (01. 29-1563) This invention relates to a method of making aeronautical propeller blades and more particularly to a method of working the metal of a solid billet so as to obtain in the finished blade the maximum strength and fatigue resistance of the metal under the stresses to which it is subjected in service.

The method consists generally of longitudinally rolling a billet of'rolled stock into the rough shape of a propeller blade by a series of one-way rolling passes toward the portion which becomes the tip in the finished blade, each pass being complete by continuing to the tip of the blade, and the series of passes serving to convert the billet or blank into a rough blade and thereby creating longitudinally extending flow lines converging at the tip and generally conforming to the contour of the finished blade. The eifect of said rolling passes progressively and gradually refines the grain structure whereby the grain size contrast is maintained at a minimum from the hub to the tip of the blade.

The method described and claimed herein constitutes an improvement overthe prior commercial methods of making propeller blades in which a billet of metal was hammer forged to rough blade shape and finished by die forging and the like. The hammer forging produces wavy irregular flow lines in the metal which are not removed in the final finishing operations so that the finished blade contains irregularities in the flow lines. each of the irregularities constituting a point at which the vibration stresses in use are concentrated, tending to start a fatigue failure in the metal. The hammer forging also produces a sharp contrast in the sizes of the grains along the cross sectional plane between the areas hammered to'difierent amounts. In the subsequent heat treatment or in natural aging the areas of sharp grain size contrast constitute areas of excessive grain growth.

It will be understood that the sizes of the grains in the metal are reduced substantially in proportion to the amount of working and the strength and other physical properties of the metal are increased by the refinement of the grain structure. During grain growth the larger grains tend to assimilate smaller adjacent grains and thereby grow and increase in size at the expense of the smaller grains. The tendency to grain growth increases with an increase-in the initial contrast between the sizes of adjacent grains. The more uniform the variation in grain size, the smaller is-the tendency to grain growth. Where the grains grow the physical properties produce by the working of the metal are lessened in proportion to the amount of grain growth.

As a consequence in the blades hammer forged to rough blade shape and subsequently finished by die forging or the like a series of cross sectional areas of excessive grain size contrast exist along the length of the blade and at these areas the grains, when grain growth occurs, increase in size out of proportion to'the other grains in the blade. These points of excessive grain growth constitute cross sectional areas of weakness in the completed blade at which failure may occur either through tensile stress or as a result of fatigue. The blade in service is subjected to centrifugal stresses, bending stresses from the reaction of the air, and vibratory stresses from the repeated explosions or application of power in the engine driving the blade which also cause pulsations in the first mentioned stresses.

A further defect associated with the prior art hammering method of making a propeller grows out of the laminations .therein caused by the presence of voids, dross, impurities, or undissolved constituents of the alloy. In hammering out a longitu' nal billet, there is less resistance to flow of the metal under the force of the hammer in a transverse direction, the area on each side of the hammer in a longitudinal direction serving to restrict the axial flow and the unsupported sides of the billet permitting free lateral fiow. When a volume of metal containing one of the above mentioned defects productive of a lamination is struck by a hammer the defect present will follow the flow of metal and thus extend transversely of the billet being worked. Regardless of the shape ultimately given the mass of the billet by hammering the lamination caused by a void or like defect frequently extends transversely of the length of the blade and thus constitutes a zone of weakness when bending stress is put upon the blade.

To overcome the defects growing out of the hammer forging method of making a propeller and to produce propellers uniformly reliable and less subject to fatigue failure phenomena it is among the objects of my invention to provide a method of making a propeller wherein the flow lines will extend generally longitudinally of the blade, will converge at the tip of the blade and will conform intermediate the ends of the blade to the contour of the propeller in its finished form. It is a further object of my invention to provide a method of making a propeller which will minimize the effect of voids, dross or impurities in the billet and which will minimize the grain size contrast, and which will effect a progressive or gradual variation in grain size from the hub to the tip portion of the blade. Further objects and advantages will appear from the following description and the appended drawing wherein:

Figure 1 is a perspective view of a billet before it is subjected to the methods hereof.

Figure 2 is a view similar to Figure 1 and develops the billet after it has been put through the first rolling pass.

Figures 3 and 4 are perspectives similar to Figure 2 bringing out the shape of the billet subsequent to further passes through the forging rolls.

Figure 5 is a plan view of a propeller after it has been roughly shaped by the forging rolls.

Figure 6 is a section taken about on the line 6-6 of Figure 5.

Figure 7 is a plan view of a finished single bladed propeller.

Figure 8 is a plan view of a finished double bladed propeller and,

Figure 9 is a showing, somewhat diagrammatically, of the forging rolls and the action of the latter on the billet, and

Figure 10 is an enlarged fragmentary view in elevation of a piece of metal which has been hammered out in accordance with the known methods above discussed.

By way of illustrating and describing a pre-- ferred specific embodiment of the invention the method of making an aeronautical propeller from an aluminum base alloy containing approximately ninety-four percent aluminum, four and fivetenths percent copper, seventy-five hundredths percent manganese, and seventy-five hundredths percent silicon, is herein set forth. It is to be clearly understood that propellers designed for' purposes other than aeronautical, and from met-- als and alloys other than that noted may be manufactured in accordance with 'the precepts of this invention without departing from the scope thereof. Not only may other aluminum base ailoys be availed of as the material from which the propellers are made but magnesium base alloys may also be employed. Such alloys have many of the properties and qualities of the aluminum al loys which render them particularly adaptable for the making of aircraft propellers. Propellers of the type noted may also be made from iron and steel, copper and its alloys, such as brass and bronze, and nickel in combined form, such as Monel metal. In fact, any metal which can be made into propellers by forging and rolling is susceptible to working by the methods of this development.

The article initially worked upon according to the'method such as is proposed hereby is shown in Figure 1 in the form of a billet or casting A. The billet A may take the form of an ingot as originally cast or a from an ingot. In the present instance the method is described, for' exemplary purposes, as beginning with the billet A, but it is obvious that the original step of a method involving rolling requires a casting operation. A preferred method of working an ingot into the billet form as depicted by the billet A is by rolling, but other operations for working the ingot into the billet may be substituted for rolling.

The billet A is formed with a handle portion or tong hold I in any suitable manner and this portion is gripped by tongs or like tools to manipubillet that has been rolled late the billet during the forming operations. After the propeller has been shaped this handle portion 1 is removed, as by cutting off.

The billet A is firstheated to a condition wherein it is readily workable, say for instance, eight 5 hundred twenty degrees F. It is then subjected to the action of the forging rolls indicated diagrammatically in Figure 9 and referred to as B. As the manufacturing processes are herein described as beginning with a billet of the shape 0 shown in Figure 1, it would not be desirable to attempt to reduce such a shaped billet to propeller shape by one rolling operation or pass through the forging rolls. A preferred rolling method comprises several of these passes which gradu- 15 ally work the billet, by successive deformings, into the shape shown in Figures 5 and 6. It is noted that rolling out operations illustrated by the change in billet form as shown in Figures 1, 2, 3, and 4 have maintained the round shape of the 20 billet and merely drawn it out into a conical for- V mation. The final pass through the forging rolls,

however, serves to flatten out the conical or tapered portion into something resembling blade shape. The conical shape of the billet after the preliminary rolling operations and the blade shape after the subsequent roiling operations are preferably obtained by suitable profiles formed on the faces of the rolls. v

The action of shaping by rolling is characterized 30 by the application of a metal deforming force which increases progressively in intensity during a rolling pass and which. also progressively advances the point of application of the force along the article being rolled in the direction of the 35 rolling. This action works the metal and therefore refines the grain structure and by reason of the uniform gradual gradient of the working force or strain, the fineness of the grains produced varies progressively without material grain size 40 contrast.

I also use the term coning to describe generally the operations which draw the billet out into a conicalformation as illustrated in Figures 1 to 4 inclusive and as described above. It will be understood that the invention is not limited to the formation of a mathematical cone or to the maintaining of a precisely circular cross section and accordingly I use the terms coning and conical shape to include all equivalent shapes and operations in which the flow lines are gathered or bunched substantially concentric about the iongitudinal axis of the billet. It will be observed that the coning of the end of the billet A remote from the handle maintains the blank symmetrical 55 -throughout its length and the elongation accompanying the coning operation positions that metal receiving the maximum amount of work toward the tip of the blade. In other words, by reference to Figure 4, the metal which is least worked 60 merges into the unworked tong handle end of the billet and thus retains the relatively coarse grain structure of the billet'whereas the other end of the cone is formed of metal worked to a greater degree and therefore has a finer grain structure. 65

double bladed propeller.

Subsequent to the coning of the billet as shown in Figure 4 the blank is flattened as indicated in Figures 5 and 6. This flattening pass is ineffective to disturb the longitudinal and converging arrangement of the flow lines and the elongation attending the flattening pass is ineflective to dis rupt the convergence of theflow lines at the tip of the blade. As illustrated in Figure 5 the flattening is substantially equal on each side of the longitudinal axis of the coned blank. This arrangement or amount of flattening with respect to the axis of the coned blank may be varied depending upon the shape or design desired in the finished article. The blank of Figure 5 may be identified as a rough blade shape and subsequent to acquiring this shape it is transferred to forging or pressing dies and further flattened and shaped.

As in the case of the rolling the blank may be heated prior to the pressing or forging operations in order to render it more readily workable.

For the purposes of this specification the various shaping operations which may be performed on the propeller after rolling are classified generally as forging. This term is intended to include any of the forming methods carried out after rough shaping in which the metal is worked by a force applied under pressure, such as forging by dies and pressing.

After the propeller has been shaped by the forging or pressing dies, it is finished by the conventional finishing processes, including cleaning, trimming and sizing. It is then heat treated by first being subjected to a temperature of about nine hundred sixty degrees F. (960 F.) for about twelve to sixteen hours, composition previously mentioned. The time is dependent on the size of the article and the amount of working the metal thereof has received, as well as the composition of the alloy. The propeller is then quenched and aged at a temperature of approximately three hundred ten degrees F. (310 F.) for about eighteen (18) hours.

Duringthis heat treatment any large grains of the metallic structure tend to assimilate and grow at the expense of any adjacent relatively small grains, since the thermal stabilityof the aggregate would be increased by an increase in grain size. By reason of the progressive variation in grain size produced by the uniform and gradual strain gradient in working, all of the grains possess substantially equal powers of orientation, and grain growth is, therefore, reduced to a minimum.

Substantially the same methods as above outlined are availed of in the manufacture of a As in the case of the single bladed article the billet is rolled from the hub or root portion, towards the ends or tips. In addition the hub portion is formed with an opening to provide for a hub mounting. This operation is preferably effected after the propeller has otherwise assumed its final form. A double bladed product is shown in Figure 8 and designated C. The latter is provided with an opening 2 as above noted.

The rolling out operations provide a product having a metallic structure that is relatively free from coarse grains, and a grain structure that is characterized by flow lines and laminations conforming in direction to the contour of the propellers, and in which the size of the grains varies I in a uniformly progressive manner throughout the propeller. Moreover, the metal is substanif the propeller be of the tially free from localized voids at the surface or extending across the blade.

To illustrate the adverseleffect with respect to flow line structure of the old hammer forging action on a billet I have showri'diagrammatically in Figure 10 how the hammer, since it extends but a small portion of the length of the billet, produces an undesirable irregularity in the flow lines. a For instance at the edge of the hammer as indicated at X there is a sharp step or juncture 1 in the direction of the metallic fibers. In the event that another hammer blow is struck above the juncture at X and overlapping both sides of the juncture another pair of irregular lines such as X will appear at each side as determined by l the edges of the hammer. This action continues blank will present a large number of transverse 20 bends or steps such as X. A hammered blank having fiow line characteristics such as indicated at X is to be distinguished from one having smooth continuous flow lines such as produced by the novel rolling method herein described.

Although I' have described one embodiment of my invention in considerable detail it will be appreciated by those skilled in the art that numerous variations may be made therein without departing from the scope of my invention. For in- 3 stance, the billet A may be cast or worked in any suitable way, although the preferred embodiment describes it as being rolled and it will also be understood that the method may be carried out upon a. double ended billet wherein the tong or 3 handle portion i is omitted and the hub portions merge into each other. Other colorable variations may be made such as employing magnesium or other alloys in casting the billet and therefore I do not wish to be limited other than by the ap- 40 pended claims;

What I claim is: p

1. The method of making a propeller blade comprising gradually deforming a billet of metal into the shape of a tapering blade by applying a 45 deforming force-to the metal, progressively advancing the point of application of force from the root portion to the tip portion of the blade, progressively increasing the force from the root portion to the tip portion of the blade to gradually 50 refine the grain structure throughout the length of the blade with a minimum of grain size contrast and to form flow lines conforming to the contour of the blade, and completing the shaping of the bladeby forging operations without increasing the grain size contrast or destroying the flow lines.

2. The method of forging propeller blades which includes heating a bar blank, elongating and coning one end portion of the bar blank by successive passes between roll dies, further elongating and tapering the elongated portion of the bar blank between roll dies, the elongated portion being worked to a predetermined size and shape during each successive pass, and then forging the partly completed product to a finished forging.

3. The method of forging propeller blades whichincludes heating a bar blank, elongating and coning one end portion of the bar blank by 7 rough blade shape, ,the

' tionof the bar blank between rolldies, theelon- .c .p aging the army Ebihbieted me t as aflnished f r in -w Y 4.;The; metho dlo forgin I} blades which includesheatinga bar blank of magnesium,-

. gated portion being worked to av predetermined size; and shape during each successive pass, and then-forging=the .partly completedproduct to a finishedforgingx; i

6-.The prnethod of forging ;-propeller blades which includes heating a bar blank, elongating andconing one endgp'ortion ofthe bar blank by successive'passes betweenroll dies, further elongating and tapering the elongatedportion ofthe bar blank between-roll dies thereby-producing a partly finished product .of slightly less width and greater thickness than desired in, the flnished blade',.the elongatedportion being worked .-to a predetermined size andshape during each successive pass, and then forging the partly completed product toa completedforging. o 'Lm'Ihe method-of forging, propeller blades which consists invheating abar; blank of light metalalloy, roll forging the barblank by a series of successiveoneeway rolling passes to elongate and cone one-end portion of; the bar blank, further roll forging the end portionto further elongate and flatten said end portion, and then forgingv the'partly completed product to a finishedforging; g: a 8. The method of forging propeller blades which consists in'heating a bar blankof; light metal alloy,:roll forging the bar blank bya series atone-way rolling passesto coneand elongate one end portion of thebarblank; further roll forging saidone end portion passes to further elongate and taper the same outwardly producing a product of slightly less width and greater thickness than desired in the finished blade, and then forging the partly completed product :to .a finished forging. if

9. The method ofroll forging a propeller blade from a billet of light metal comprising subjecting the billet to a series of rolling passes to elongate and taper one end of the billet-into a substantially conical-form, further rollingthe billet to further elongate and flatten the-same into a roughblade'shaperand completing the shaping of the blade by operations maintaining the fiber and flow line structure created by said rolling.

10. The method of roll forging-a propeller blade from a billet=of light'metal comprising subportion Ihe e t qn maz

jecting the billet to a seriesof one-way rolling passes to elongate and taper one end of the billet into-asubstantially conical form, further rolling the' billet to further elongate and flatten the same into substantially the shape of the finished blade, and completing the shaping of and finishi'ngthe blade.

;-. 1l. That method ofmaking a propeller which comprises rolling a cone at one end of a cylindrical blank to elongate same and establish longitudinally extending flow'lines converging at the coned end thereof, exerting pressure on the coned blank to flatten the same to form a blade with the longitudinally extending flow lines conforming to the contour of the blade and the converging lines terminating at the tip of the blade.

which comprises rolling a cylindrical blank, rolling a cone .with its apex disposed at that end of the blank which forms the tip of the blade in the finished article to effect a progressive decrease in grain size frorn the hub to the tip of the blade, exerting pressure on the coned blank to flatten the same without disturbing the resultant grain size arrangement or the flow lines extending longitudinally of the blank.

'13. That method of making a propeller blade whichcomprisesrolling a cylindrical rolled stock billet to form a blank having a gradually decreasing' diameter an' d a substantially round cross section and an axial extent exceeding the length of the originalcylindrical billet whereby the grain structure is characterized by gradually decreasing grainsize from one end of the blank to the fect a progressive dia'meterlreduction toward one end and simultaneously elongate the blank by progressively increasing the deforming force near said end,cs aid rolling action maintained on all sidesofthe blank toresult in an elongated conical blank withthe distribution of the mass of the metal corresponding. to the mass required throughout the axial extent of the finished propeller, said rolling action also effective to establi s h longitudinally extending flow lines converging in that areawhich becomes the blade tip in the. finished article, exerting pressure on the conical,blank to shape the same into rough blade shape in a manner to maintain said flow line arrangement. no

1 5. The method of making a metal propeller which includes rolling a blank of metal longitudinally to effect a tapered cone at one end by a .series .of one way rolling passes, thereafter flatteningthe coned blank into a blade of rough propeller form by subjecting; it to further rolling passes extending in direction from the hub to the ,tipfand thereafter, further-shaping the rough propellerformby die forging or pressing opera- A. HANDLER.

f 12. Q'Ihat, method of making a propeller blade 5 CERTIFICATE OF CORRECTION.

Patent No. 2,044,293. June 16, 1936.

ALFRED A. HANDLER.

It is hereby certified that error ap peams in the printed specification of the above numbered patent requiring correction asfollows: Page 1, second column, li e 1, for the word "produce" read produced; page 4, first 001-- umn, line 49, claim 8, strike. out the word "passes"; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office,

Signed and sealed this 15th day of September, A. D. 1936.

Henry Van Arsdale' L (Sea1) Acting Commissioner of Patents. 

